Dr. VishwJS S. Kale Reader in Geomorphology, Deptlrtm:!)t of Geography, UN IV U:::;I'[ '.' OF POON A rUNE-411.007. : INDIA) TEMPORAL AND SPATIAL DISTRIBUTION OF SEISMIC CASES IN THE DECCAN PENINSULA OF INDIA V. S. KALE and S. N. RAJAGURU General The Deccan.. Peninsula of India has been considered as a stable Shield for a very long time. No earthquakes and tremors of high magnitude were registered in the past, from any part of the Peninsula. Therefore, the entire shield was regarded as "aseismic" by early earth scientists. However, the devasting earthquake of Koyna in 1967, which regis- tered a magnitude of 6.5 to 7.0 on the Richter scale, has totally terminated the earlier views and concepts. Such high seismicity was consi- dered anomalous in this area, once regarded as a stable block. The Koyna tremors trig- gered extensive and detailed seismological and geophysical studies in this part. These investigations have brought in enough evi- dences to refute the earlier beliefs. Deccan Peninsula as a Seismic area Information about the earth tremors obtained from various historical and scien- tific records, indicate that the seismic cases were not unknown in the Peninsula. The data reveal that a good number of earthquakes have been experienced in the past four hundred years (vide Table I & II). None of these were, however, severe and devasting. Hence, not much importance was attached to these mild and micro-level seismic cases. But the sudden spurt of major seismic activity at Tambaram (Madras) in 1966, at Koyna in 1967 and subsequently at Bhadrachalam in 1969, at Broach in 1970-72 and at Khardi in ' 1983, has established the seismic nature ofthe Peninsular India. A. TEMPORAL DISTRIBUTION OF THE SEISMICITY Historical records reOect that the earliest instance of the earth tremor in the Peninsula, has been in the year 1541. This quake was experienced al0ng the Malabar Coast. The catalogue of the earthquakes in India and bourhood (1983) prepared by the Indian Society of Earthquake Technology- Roorkee, records tremors for the year 326 . B. C. The epicentre of this tremor was not, however, located in the Shield area, but off the Karachi coast. Compilation of historical data reflects that between 1541 and early 1960's more than fifty perceptible tremors have been registered in the various parts of the Deccan Shield (vide Table I & II and Fig. I). During the early sixties of this century a network of sensitive seismographs was estab- lished in Western Maharashtra and in other parts of the Peninsular India. Since then a detailed record of the seismic activity has been preserved. These seismological records illus- trate that during the last two decades over 200 major shocks and more than 30,000 micro- level seismic cases have been registered in the Peninsula (Mohan et. al. 1981). Although, a collation of the seismic activity before and after 1960's is not possible because of the inadequacy of the data, some interest- ing inferences can be drawn. In the first place, it is evident that no severe tremors had been scientifically recorded before the devasting earthquake of Koyna of